The invention relates to a fuel injection system for mixture-compressing internal combustion engines having externally supplied ignition.
In a known fuel injection system of this type (German Offenlegungsschrift 31 09 559), the differential pressure valve has two chambers divided by a valve diaphragm, which at the same time embodies the valve member; of these chambers, the one containing the valve outlet communicates with the metering slits, while the other has introduced into it the same control pressure that acts upon the control piston of the metering valve. As a result, the metered fuel quantity is determined by two variables, namely the position of the control piston and the opening cross section of the metering slits that is uncovered thereby on the one hand, and the pressure differential at the uncovered cross section of the metering slits on the other. The product of these two variables determines the total influence exerted and thus the fuel metering.
Although a control ratio of greater than 1:30 for the metered fuel quantity, despite a relatively low control ratio between the system pressure and the control pressure, can advantageously be attained with a known fuel injection system of this type, there is nevertheless the attendant disadvantage of nonlinear and unpredictable control characteristics.